<PRE><B>Question 906630</B>
motorboat maintained a constant speed of 15 miles per hour relative to the water in going 10 miles upstream and then returning. The total time for the trip was 1.5 hours. Use this information to find the speed of the current.
***
let c=speed of current
15-c=speed of boat upstream
15+c=speed of boat downstream
travel time=distance/speed
..
{{{10/(15-c)+10/(15+c)=1.5}}}
150+10c+150-10c=1.5(15-c)(15+c)
300=1.5(225-c^2)
300=337.5-1.5c^2
200=225-c^2
c^2=25
c=5
speed of current=5 mph</PRE>